Earlier this year Dr Jean-Philippe Chaput and I published an editorial in the journal Bioenergetics: Open Access examining whether weight gain should be seen as a physiological problem or as merely a logical adaptation to our current environments.

JP is a prolific researcher and writer, so it was a lot of fun to be able to work with him on the paper (he gets the vast majority of credit for the article – I was very much the second author on this one). JP is also a collaborator on several of my thesis projects, and I’m looking forward to sharing some of our other work in the near future.

Since the article is open access, I have re-published it in full below. The original article with citation information can be found here. And for more on this topic, be sure to check out JP’s recent paper in Obesity Reviews titled Obesity: A Disease or a Biological Adaptation.

Bioenergetics of Obesity: Is Fat Gain a Problem or a Solution?

According to the first law of thermodynamics, fat gain is the result of a positive energy balance (i.e. energy intake > energy expenditure) [1]. When an individual experiences a chronic positive energy balance, this can lead to the accumulation of excess body fat, and ultimately obesity. Obesity rates have increased so dramatically among industrialized countries in recent decades that it has been referred to as a “pandemic” [2]. Attenuating these high rates of obesity is a high priority in many countries not only from a population health perspective, but from a health care system’s economic perspective [3]. However, reversing this trend is a herculean task and will likely require a major change in societal norms and the values underlying those norms [4,5].

A major challenge of today’s world is that our so-called “obesogenic” environment is conducive to the consumption of energy and unfavorable to the expenditure of energy, therefore predisposing to a chronic positive energy balance. The modern, money-oriented, computer-dependent, sleep-deprived, physically-inactive human lives chronically stressed in a society of food abundance. From a physiological standpoint, the excess fat gain observed in prone individuals is perceived as a normal consequence (i.e. biological adaptation) to a changed environment rather than a pathological process [6]. In other words, weight gain is a sign of our contemporary way of living or a “collateral damage” in the struggle for modernity [7].

Body fat, when kept to an appropriate level (probably defined by an individual’s genetics), is a necessary and healthy energy reserve. Recent evidence suggests that while fat stays in the fat cells, for which they are designed, there is little cause for concern [8]. Body fat begins to cause metabolic problems only when lipid-intolerant nonadipose organs are not protected against lipid “spillover” during sustained energy surplus [9]. In fact, it is increasingly recognized that it is visceral fat and the fat deposited “ectopically” in organs like the liver, pancreas, heart or skeletal muscles that tends to cause increases in cardio-metabolic risk [10]. Interestingly, the accumulation of fat under the skin (i.e. subcutaneous adipose tissue), which is less lipolytically active than other fat depots and therefore able to safely sequester fat away from ectopic depots, seems to be associated with reduced cardiometabolic risk [11,12].

1. What are the Benefits of Body Fat Gain?

Obesity, at least when operationally defined as exceeding a specific amount of body fat and/or body mass index, is associated with certain health benefits. Examples include the now rarely needed but obvious protection against starvation in times of food scarcity, protection against osteoporosis, fractures, frailty, and premature mortality in the elderly, as well as reduced mortality rates in the face of certain severe illnesses or injuries [6]. The assumption that adiposity per se increases mortality risk is also not well supported by the scientific evidence. Many epidemiologic studies have shown that people who are overweight or moderately obese live at least as long as normal weight individuals, and often longer [13–15]. Additionally, life expectancy increased dramatically during the same time period in which body weight rose, and the World Health Organization projects life expectancy will continue to rise in coming decades [16].

From a physiological standpoint, fat gain is seen as a solution for maintaining homeostasis and re-establishing energy balance in the current obesogenic environment. The ability of fat cells to produce molecules involved in genuine regulatory processes has been known for decades. During weight gain, many adaptations over time can promote the re-equilibration of energy balance. These include increases in fat oxidation, sympathetic nervous system activity, insulinemia at euglycemia, leptinemia, and overall energy expenditure [6]. The problem related to fat gain as a physiological compensation to chronic unhealthy lifestyle habits is that it cannot occur with the same metabolic efficiency as exercise. Specifically, fat gain relies more on increased concentration of substrates (e.g. free fatty acids) and hormones (e.g. insulin and leptin) to re-establish energy balance by increasing total energy expenditure, which likely underlies the occurrence of the metabolic syndrome which often accompanies obesity. Thus, while increasing fat reserves may help to restore energy balance, it can also lead to increased risk of chronic disease. These observations emphasize the importance of adhering to a healthy lifestyle in order to maintain body weight stability rather than relying on the overuse of regulatory systems.

2. What are the Adverse Effects of Weight Loss?

Although counter-intuitive, many prospective observational studies suggest that weight loss increases rather than decreases the risk of premature death [17–19]. Paradoxically, most short-term weight loss intervention studies do find improvements in many health indicators. However, given that intentional weight loss is generally accompanied by a change in dietary and physical activity behaviors, it is not known whether or to what extent the improvements can be attributed to the weight loss per se. The case of liposuction can certainly provide relevant information about the effects of subcutaneous fat loss in the absence of behavior change. In their study, Klein et al. [20] evaluated the effects of large-volume abdominal liposuction on metabolic risk factors in obese women before and 10 to 12 weeks after liposuction. Although the participants lost 10.5 kg of fat, liposuction did not improve obesityassociated metabolic abnormalities, suggesting that decreasing adipose tissue mass alone (and especially reducing subcutaneous fat stores) without behavior change will not achieve the metabolic benefits of weight loss. In contrast, most health indicators can be improved through changing health behaviors, regardless of whether weight is lost or not. For instance, it is well-known that physical activity participation without weight loss has the capacity to reduce visceral adiposity and substantially improve the cardio-metabolic risk profile [21]. Similarly bariatric surgery, which dramatically changes the way that food is consumed and digested, has been shown to result in rapid improvements in glycemic control just days after surgery, long before any appreciable weight loss has taken place [22]. These observations agree with the “fat but fit” [23] and “metabolically healthy but obese” [24] concepts and stress the importance of regular physical activity and a healthy diet as key components in any health promotion and disease prevention strategy, regardless of body weight.

Moreover, attempts to sustain weight loss invoke adaptive responses involving the coordinated actions of metabolic, neuroendocrine, autonomic and behavioral changes that oppose the maintenance of a reduced body weight. The multiple systems regulating energy stores and opposing the maintenance of a reduced body weight illustrate that body energy stores and fat stores in particular are actively “defended” by interlocking bioenergetic and neurobiological systems. The fact that more than over 80% of individuals return to pre-weight loss levels of body fatness after otherwise successful weight loss certainly illustrates this “sad” reality [25], whereas studies of people successful at sustained weight loss indicate that the maintenance of a reduced degree of body fatness requires a lifetime of meticulous attention to energy intake and expenditure [26]. Among the adverse effects of weight loss, it is well-known that body fat loss complicates appetite control, reduces energy expenditure to a greater extent than predicted, increases the proneness to hypoglycemia and its related risk towards depressive symptoms, increases the plasma and tissue levels of persistent organic pollutants that promote hormone disruption and metabolic complications, and increases psychological stress, all of which are adaptations that significantly increase the risk of weight regain [27].

Concluding Remarks

The general perception of obesity today is more pessimistic than optimistic with words like “global epidemic”, “important problem” or “scourge” that are omnipresent in the popular media as well as in the scientific community. The corollary of this widespread message is obviously a greater pressure on obese individuals towards weight loss. However, an accumulating body of evidence suggests that a focus on weight loss as an indicator of success is not only ineffective at producing thinner, healthier bodies, but also damaging, contributing to food and body preoccupation, repeated cycles of weight loss and regain, reduced self-esteem, eating disorders, and weight stigmatization and discrimination [28]. It is thus time to shift the focus away from body weight and center our efforts on the promotion of a healthy lifestyle if we really want to have an impact on the health of the population in the long term and reduce the burden on individuals with obesity.

Our better understanding of obesity, as witnessed by an impressive amount of publications in the field over the last decades, suggests that body fat can be both detrimental and protective. Simplistic messaging that body fat is “bad” and weight loss is “good” for our health can be misleading and ignores the truth about the biological response and side effects of weight loss, as well as the importance of fat gain in maintaining body homeostasis in a “toxic” environment. Fat gain is part of a regulatory strategy that permits the recovery of energy balance and body weight stability in a world that has increasingly added obesogenic factors to our lifestyle over time. In this context, a preventive approach that includes healthy lifestyle habits and that attempts to reduce the obesogenic nature of our society is the only long-term viable solution to maximize our health, even if it does not easily fit within the priorities of an economically globalized world.

Acknowledgements

Dr. Chaput holds a Junior Research Chair in Healthy Active Living and Obesity Research. Mr. Saunders is supported by Doctoral Research Awards from the Canadian Diabetes Association and the Canadian Institutes of Health Research, as well as an Excellence Scholarship from the University of Ottawa.

About Travis Saunders, Phd, MSc, CEP

Travis Saunders has a PhD in Human Kinetics, and is currently an Assistant Professor in Applied Human Science. His research focuses on the relationship between sedentary time (e.g. sitting) and chronic disease risk in both children and adults. He is also a Certified Exercise Physiologist and (former) competitive distance runner. You can connect with him on Twitter @TravisSaunders.

35 Responses to Is Fat Gain a Problem or Solution?

Travis… I love you. Thank you for this. As a weight-stable, physically active, metabolically healthy woman who is either “overweight” or “obese” depending on how much clothing I am wearing, I thank you from the bottom of my heart.

I intend to send it to my employer’s wellness program in yet another one of my attempts to get them to become less weight-focused.

Ditto the thanks! To the extent that obesity is an actual problem, (which this article debates), I am reminded of that Einstein quote about how you cannot solve a problem by working within the same mind-set that created the problem. We really need new perspectives and new ways of thinking (about this and many other modern problems), and this article is a fascinating new perspective. I’ll be sharing this one around!

Very nice job on the article, it expresses that viewpoint very clearly.

In addition, I suggest that even if we ignore for the moment anorectics and their distinctive neurological and psychological responses and also people with low visceral fat or no risk factors related to obesity, we can still possibly save the OTHERS who are at legitimate health risk from blindness, amputations, and early death even if at the cost of them being a little obsessed with their body until their new habits have become ingrained. I think that is a pretty good tradeoff in most cases. Especially since that’s the way we learn most things that are hard to do at first. Temporary obsession with our body in order to make healthy lifestyle changes is a whole different thing from the chronic addictive patterns of people with eating disorders.

I was about to go on oral anti-diabetic meds and I decided instead to become a “little obsessed” with lowering my HgA1C by changing my own environment, and it indeed went steadily down as my “obsession” helped me to adapt to a lower glycemic and higher activity lifestyle. It became easier over time once the habits began to change and I found increasingly more variations of the same nutritional and activity strategies. Several yrs now of overall progress with inevitable ups and downs and I have been able to back off gradually from the deliberate focus and “obsession” as the healthier habits became easier and I learned to respond more reasonably to the inevitable backslides and get back on target. I don’t think this is beyond the grasp of the many other people in the same situation if they are similarly motivated and are given the same tools.

I think if I were in this field I would be trying like hell to figure out how to leverage our natural habit formation and learning patterns to help people change in a positive way. I had to figure it out on my own over time from the mess of conflicting information available and ignore the advice of nearly everyone, since even most experts seem to greatly overestimate their own knowledge of health and fitness due to the complexity of the underlying topic.

Importantly, I think long term success usually means big changes, not just little convenience nudges. I see mostly people making the mistake of just trying to make it easy to get in a little more activity. Nothing wrong with making it easier to do the right thing in principle and it has its place, but you also have to prepare for significant difficulties at first, changing the way you think about eating and activity decisions. You can’t expect to make major permanent changes just by convenience nudges alone. That’s like expecting people to lose body fat by burning off a couple more calories a day and eating a couple of calories less a day. We know that doesn’t work, as the article points out, because various regulatory mechanisms oppose those kinds of gradual subtle changes over time. We eventually find ways to defeat those little changes.

We need to provide the tools for people to focus on bigger and more clinically meaningful changes until they become new habits.

So I would be interested in learning from the 20% who succeed in the long run and applying those lessons more broadly, and personally I would be averse to telling the other 80% that they are just normally adapting to a bad environment and shouldn’t worry about it.

When you aren’t achieving your objectives, you can lessen your dissonance either by improving your methods or changing your objectives. But I don’t think we should give up on objectives just because they are difficult to achieve or because most people don’t seem to manage it. There are a lot of examples of initially difficult cultural changes that started with a tiny minority and became widespread over time.

Agree with the final conclusion and weight per se should not be the focus of health, but for a significant number of people it does serve as a reasonable proxy until they come into a reasonably healthy range for their own risk factors. I am disappointed when I see professionals giving up on people because of statistics. There are a lot of reasons why people fail to achieve things important to them. For example we don’t have direct control of our own implicit priorities, we have to find indirect ways to change ourselves.

I suspect there are still ways of improving our success rate against widespread unhealthy forms of obesity without compromising on our objectives.

Thanks. I think this is a great article and expresses an argument very clearly the nuances of which are not often explored in popular media. I hope others pick up on this and your article gets wider circulation.

Thanks also for your work on this blog. I read it quite regularly, although this is the first time I’ve commented.

This is a bit of a tangent, but I wonder how you guys stand on the concepts promoted by people like Gary Taubes and Robert Atkins, that refined carbohydrates (especially processed sugar) are themselves a biochemical signal that promotes fat gain? The above article discusses the “thermodynamic” perspective, that energy in equals energy out plus fat storage. Your above article does not _deny_ that the real picture is more complicated than that, but I wonder what you think about Gary Taubes’ work.
No doubt you have some idea of what Taubes and Atkins say, but for other readers I’ll recap that the “energy in/energy out” balance is complicated by the fact that it relies on hormonal processes — most significantly, the insulin response — and not everybody’s insulin system is alike, and the insulin system does not react at all the same way to caloric energy ingested in the form of refined carbs (e.g. sugar) as it does to caloric energy ingested as proteins or fats.
Taubes receives some [rightful] criticism for slanting his writings to make it seem like carbs and insulin are the _only_ things governing fat accumulation. But in my opinion, if you read his stuff, he agrees that the only way to get rid of fat is to expend energy. The problem is that a chronic, abused insulin response can, in some people, overwhelm such expenditures, clinging tightly to fat instead of giving it up. Taubes’ work tries to explain things to an audience of people who have tried exercise and not gotten results or seen the weight come rapidly back. The “energy in/energy out” model has no means to explain the cruel unfairness of watching some people we all know, who eat tons of junk food, never exercise and still stay thin. The focus on the insulin response explains it, because everybody’s hormonal systems are different; some are more sensitive or fragile than others. It also explains why young people who eat junk food and don’t exercise can often remain thin while young, but quickly start packing on the fat in middle age — because peoples’ hormonal systems change over time.
If fat were just a matter of “energy in/energy out”, then everybody should achieve the exact same results from the same diet and the same exercise, regardless of age, sex, or other personal factors. Taubes writes in an aggressive style because virtually all of us know from our own experience that we _don’t_ get the same results, but the medical establishment refuses to acknowledge this. (Just in the last few years, though, I see signs that the conventional wisdom is finally coming around.)
This could [hopefully] be the subject of a whole ‘nuther blog entry from you. It’s a tangent from the above, so sorry for the thread hijack. But although I was excited to read this article and I have already circulated it to a bunch of friends, this article’s reliance in the first sentence on the “energy in / energy out” model rubbed me a bit the wrong way.

Thomas, I agree with the suggestion that regulation and changing tissue sensitivity to insulin turn out to be a much bigger factor in bodyfat accumulation than most influential experts recognized for a long time. Part of a larger, more complex cluster of phenomena, but definitely not one to be ignored. The article’s start is an odd rhetorical device I think. Thermodynamics doesn’t adequately explain obesity technically, because there is no practical way to isolate the living body to a closed thermodynamic system, it constantly exchanges energy and matter with the environment and transforms matter and energy in ways that we can only grossly measure. That’s why other authors have tsken on the metabolic model instead. I think the reality is that they each capture important aspects of body mass regulation. We do care about matter taken in and excreted and we. do care about activity levels representing conversion of chemical energy, but we also care about the details of metabolism and body composition because they strongly shape the rates at which and manner in which those black box thermodynamic processes occur.

Good question. I’ll preface this by saying that I haven’t read Taubes’ work in detail, and that these comments are speaking only for myself.

I’d say that generally I agree that not all calories are equal, and there is some good evidence that spikes in insulin can cause all sorts of havoc. I’ve heard Bob Lustig speak on the issue and read a lot of his work, and I think there’s something to it. But as you say, Taubes seems to position this as the *only* cause of obesity, which I think is a little shortsighted to say the least.

Just to be clear, at the end of the day weight really must come down to energy intake vs expenditure. The thing that people often forget is that energy expenditure encompasses more than just physical activity (e.g. resting metabolic rate, non-exercise activity thermogenesis, etc). So there may be conscious or unconscious compensation to increases or decreases in exercise which may make it appear that energy intake < energy expenditure. That doesn't really help in a practical sense, but I think it's an important thing to keep in mind that we can never cheat the laws of thermodynamics – we just may have less control over some aspects of energy balance than we'd like.

If there is something to the Taubes/Lustig argument, it is that it helps to create a situation where energy intake < energy expenditure more effectively than simply focusing on eating less and exercising more.

I think you may enjoy the following paper, which looks at these issues in detail:

So there may be conscious or unconscious compensation to increases or decreases in exercise which may make it appear that energy intake < energy expenditure.

Just realized that sentence doesn’t really make sense. Meant to say that although if someone exercises more it may make it appear that now energy intake < energy expenditure, compensation may occur in non-exercise activity thermogenesis or resting metabolic rate so that total energy intake and expenditure remain in balance, preventing weight loss.

Thanks, that Nature article seems to capture many of the concerns very well. The emphasis on “thermodynamics” often in practice leads to ineffective programs that don’t take satiety, insulin sensitivity, or varying metabolic state into account and I think very likely has contributed inadvertently to the problem by supporting mostly bad ideas like diet sodas, low fat high glycemic diet snacks, and inadequate fiber, protein, and water intake. If you take the arguments in this article seriously, it is clear why you can’t treat energy balance as the guiding principle for body fat regulation. Rather it is one importnt constraint among others, one that requires u to do reasonable portion control and stay active. Rather than just expecting to cut a few calories per meal in any random way and tke a few steps a day more and expect that to have any substantial effect for more than a few weeks under great effort to compliance. We have to work with the principles of metabolism, nutrition, and satiety, in other ords, our biology, not just thermodynamics.

Thanks to you both for thoughtful responses — I haven’t yet read the Nature article, but I’ll open it right now. Taubes and Atkins can certainly be polarizing figures and I’ve seen a lot of criticism against them, particularly from nutritionists, which just seems rather emotional and does not appear to address the major points. A lot of people — both non-experts and also nutritionists — seem to take Taubes’ theory as offering some kind of “license” to fat people who “need” to be “disciplined” with exercise and strict diets, whereas in my opinion that’s not what he’s saying at all.
I felt pretty sure I’d get a civil, rational reply here, having read your blog for something like a year now, and you have not disappointed. I’ll look forward to you posting on this in the future! Be prepared for some lively commentary from other nutritionists, though!

Somewhere 40 years ago or so we went off the rails. Suddenly the energy balance equation got turned backward and phrases like this began to appear:

“Just to be clear, at the end of the day weight really must come down to energy intake vs expenditure. ”

I know you mean well and certainly everyone agrees with the first law of thermodynamics, however, this just isn’t how it’s expressed in the human metabolic system. The obesity issue isn’t because we ‘eat too much and exercise to little.’ As any basic endocrinology medical text has pointed out for 70 years adiposity ( the disposition of fat in the body ) is regulated in the body by hormonal processes. We know this. It’s not some new knowledge. Yet, here we are now 40 years along with this misleading use of Newton’s first law. As Robert Lustig of UCSF Medical ( and others like Science writer Gary Taubes ) has pointed out, it is not “if you eat it you better burn it, or you will store it.” instead the case is ” if you store it, you better burn less, or eat more.” the

The issue is discussed in a video of the UCSF seminar given why Dr Robert Lustig that went viral last year and can be found online on YouTube. An article in the New York Times Magazine gave an excellent account recently.

My point, by the way, is that even sedentary people in the past weren’t gaining fat like that have since 1970 onward. We should try to understand what has changed that caused an increase in the regulation of bodily fat disposition and a reduction in appetite suppression. Why many of us do our best attempt to rely on problematic epidemiological work I think that recent ‘experimental’ science is beginning to show us the cause.

I think you might have misunderstood what I was saying. The metabolic/hormonal system we’re talking about still affects energy balance – that’s how it can reduce body weight. This doesn’t contradict anything that Taubes or Lustig are saying, it’s just the mechanism through which their hormonal arguments can affect body weight.

Consuming foods that lead to insulin or leptin resistance might cause us to consume more or expend less calories, therefore causing weight gain (just as the hormonal folks argue). So focusing directly on eating less or exercising more (they would argue) is a useless battle until you get the insulin resistance under control. Once you’ve cut out the foods that are causing the insulin resistance then energy balance largely takes care of itself. So the argument is simply that by focusing on the *type* of calories we do a better job of regulating energy balance than by focusing on the *quantity*of calories. They’re not saying that energy balance doesn’t matter, just that’s it’s more effective to focus on the hormonal factors that regulate energy balance, rather than trying to tinker with energy balance directly by cutting food intake or exercising more.

I’d also point out that my one primary problem with this line of reasoning is that people (Taubes especially) often present this hormonal side of things as the *only* cause of obesity. I think it’s a big cause (in a recent review paper I pointed to sugar sweetened beverages as being a key driver of the obesity epidemic, for the same reasons pointed to by Taubes and Dr Lustig) and one that is worth examining in individuals who are looking to improve their health, but it’s not the only factor causing people to gain weight.

As a full-time employee at a senior care facility, I can say from first-hand experience that weight gain has absolutely no positive effects on the elderly. Obese residents are typically bound to their motorized carts for mobility, require assistance with simple tasks such as undressing and getting into bed, reliance on carts and walkers atrophies their muscles and cardiovascular system and when they do fall, they have absolutely no hope of getting up. From what I can tell, and what I’ve been told, their day to day life is one of futility and misery. Perhaps a middle-aged person can get away with additional fat gain, but it is not advised for entering old age.

My criticism of obesity is more moralistic than scientific (perhaps even bordering on self-righteousness). Obesity doesn’t exactly foster the kind of productive, disciplined lifestyle that is so crucial in the contemporary world. To me, obesity is like a smoking addiction: you can get away with it, and realistically it will probably only take 5-10 years off of your life, but it affects your quality of life, and it ultimately breaks your spirit to spend a lifetime wrestling with feelings of powerlessness and lack of self-control.

To be clear, when we talk about the “benefits” of weight gain we are speaking of homestatic benefits. In other words, the body is getting itself into energy balance. This of course may have other unwanted side effects. We’re specifically *not* talking about benefits to health or quality of life – it’s pretty clear that obesity does not improve ones quality of life.

I agree that your view of obesity is self-righteous. I don’t know many people who have “chosen” to be obese, but know many who would “choose” not to be, if it were so simple. If it were simply about self-control, then it would be hard to explain the dramatic increases in body weight over the past century.

Keith – your perspective may be skewed by the fact that you are working with a population in need of a great deal of care to begin with. If I worked in a hospital ward where I was nursing people through the delirium tremens, I’d probably have a much worse opinion of alcohol than if I were around a normal crowd of people at a party with varying levels of sobriety & intoxication.

I cringe at the implication you make that because my BMI number isn’t in the “correct” range that I’m somehow living a powerless, out of control, unproductive life. I assure you, I am not.

Travis, I think your perspective on ths s very resonable. It might help to distinguish (1) the principle of “energy balance” in the thermodynamic sense, which is obviously true if you could account for all matter and energy and transformations involved, and (2) the application of that principle in spite of metabolic considerations, which is what many are arguing against. That is I think what produced the mostly failed ideas of just eating less of everything and cutting out dietary fats. If you take both metabolism and energy balance into account you get a better model than either in isolation.

“…life expectancy increased dramatically during the same time period in which body weight rose, and the World Health Organization projects life expectancy will continue to rise in coming decades [16] ”

Also, this sort of false correlative doesn’t strengthen the argument for obesity. Using my admittedly limited knowledge of medicine and statistics, I would assume infant mortality rates have a much greater impact on life expectancy than obesity. Unless you were referring to a more specific type of life expectancy in the aforementioned sentence, it is a misleading connection. Because we have improved infant mortality rates worldwide in the 20th century with vaccinations and other medical breakthroughs, our life expectancy rates have gone up dramatically, and will probably continue to do so. The fact that we’ve also seen a rise in obesity is probably not connected at all.

When we breathe , we are CHANGNING the numbers of atoms /molecules in our bodies.

Lyle McDonald’s equation is WRONG.- LAUGHBALYWRONG and simplsitic.

I have VERIFIED this from TOP guys at Harvard.

There is NO caloric energy being turned into matter in a human. Caloriesd are a measurement of heat outoput from BURNING a substance in a bomb calorimeter. They have VERY LITTLE to do with BIOCHEMICAL PROCESSES of the human body WHICH ARE NOT EVEN REMOTELY similar to combustion.

About the Authors

Peter Janiszewski has a PhD in clinical exercise physiology. He's a medical writer/editor, a published obesity researcher, university lecturer, and an avid traveler. You can connect with Peter on Twitter. For more information please visit his website.

Travis Saunders has a PhD in Human Kinetics, and is an Assistant Professor in Applied Human Science. His research focuses on the relationship between sedentary time (e.g. sitting) and chronic disease risk in both children and adults. He is also a Certified Exercise Physiologist and competitive distance runner. You can connect with Travis on Twitter and Google+.

Disclaimer

The opinions expressed here belong only to Peter and Travis and do not reflect the views of any organization. Any medical discussion on this page is intended to be of a general nature only. This page is not designed to give specific medical advice. If you have a medical problem you should consult your own physician for advice specific to your own situation.